The present invention relates to writing instruments in general, and more particularly to a writing instrument having a mechanism for advancing and retracting the writing tip of the instrument wherein the mechanism is actuated by rotation of a knob disposed at the non-writing end of the pen barrel.
Various writing instruments such as pencils or ball point pens are known in the art wherein the writing tip is advanced or retracted relative to the barrel by means of rotating or pushing the external element on the barrel of the instrument. Typical of such advance-retract devices are to be found in U.S. Pat. No. 3,679,318, issued Jul. 25, 1972, to Thomas A. Liguori; U.S. Pat. No. 4,290,706, issued Sep. 22, 1981, to Tatsuo Ariga; U.S. Pat. No. 4,786,197, issued Nov. 22, 1988, to Harold E. Koeln et al.; French patent 1004813, published Apr. 3, 1952, in the name of Poursier; and British patent specification 934160, published Aug. 14, 1963, in the name of Ronald Hare. These, as well as other devices have been disclosed, and many mechanisms of this type have been produced, and have met with commercial success.
One such device is disclosed in co-pending U.S. patent application Ser. No. 08/107,519, filed Aug. 17, 1993, in the name of William B. Tucker, and assigned to The Gillette Company now U.S. Pat. No. 5,342,135. In that application, a writing instrument is provided that includes an advance-retract mechanism serving to project the writing tip from within the barrel for employment of the writing instrument, and to retract the tip to a point within the barrel when the writing instrument is not in use. A plunger assembly includes a rotatable knob which is disposed at the rear of the barrel and is interconnected to a finger which contacts a cam surface of a slidable actuator. Rotation of the knob in one direction advances the writing tip from within the barrel, and opposite rotation of the knob is effective to retract the writing tip into the barrel.
While the structure disclosed in the above-referenced application has proved successful in accomplishing its various objectives, it is considered that improvement of the knob attachment to the shaft of the plunger assembly may be accomplished by more firmly fixing the connection between the rotating knob assembly to the rotating shaft of the plunger assembly, while increasing the ease of rotation of the knob during the actuating process.
It is therefore an object of the present invention to provide a writing instrument of the type described wherein the rotatable shaft portion of the actuating mechanism which extends into the rotatable knob is more firmly affixed to the knob while further providing a more easily rotatable knob for actuating the mechanism.
A further object of the invention is to provide a retainer and bearing assembly which is mounted at the rear of the writing instrument barrel and is effective to firmly affix the shaft of the advance-retract mechanism onto the barrel while providing for ease of rotation of the actuating knob.
A further object of the invention is to provide, in an alternative embodiment, a retainer which is mounted at the rear of the writing instrument barrel and is effective to firmly affix the shaft of the advance retract mechanism onto the barrel while providing for ease of rotation of the actuating knob, without the use of a bearing assembly.